1. Field of the Invention
This invention relates to a method and apparatus for feeding and assembling pins into holes prepared in circuitized carriers for ultimate use in electronic packages.
The pins are electronically conductive, typically comprising gold or copper on at least an electrically continuous surface, and having been affixed in place through holes in a first major surface in a circuitized carrier, such as a semiconductor chip, printed circuit board, and the like, emerge from the opposite, i.e. second major surface where they are available for further processing, such as soldering to conductive regions on a surface or within prepared holes in another circuitized carrier. In this manner, compact and efficient electronic packages can be constructed.
2. Background Art
In the past, small shaped objects have been supplied from a vibratory bowl or an inline horizontal vibratory feeder or a belt/cam feeder often through a series of tubes to a shuttle mechanism and then into a carrier. Examples of the rotary bowl type vibratory feeder are described in U.S. Pat. Nos. 3,907,099, 4,348,806, 3,295,661, 4,383,359 and 4,206,539. An example of an inline horizontal vibratory feeder is described in U.S. Pat. No. 4,821,864. Examples of mechanical belt/cam feeders are described in U.S. Pat. Nos. 2,675,120 and 2,433,010.
The feeders described in the existing art are intended to handle a variety of parts. For example, feed of oriented parts having heads is described in U.S. Pat. Nos. 3,907,099, 2,433,010, 4,348,806, 4,821,864 and 3,295,661. Feed of oriented parts of a variety of shapes is described in U.S. Pat. Nos. 4,383,359 and 4,206,539. Feed of granular food particles is described in U.S. Pat. No. 2,675,120. In contrast, the pins fed in the present invention are conductive, headless pins substantially identical to one another and not oriented prior to feeding.
Two methods of delivering parts, such as conductive pins, into a carrier, such as a printed circuit board or semiconductor chip, have been used. The first method employs a full matrix of tubes positioned over the carrier wherever the predetermined pattern requires a pin. The pins pass through the matrix of tubes from a vibratory feeder, and the flow of pins from the tubes is periodically interrupted by a shuttle mechanism.
The second method, a row by row scan drop method, employs only a single row of tubes leading from a vibratory feeder at one end and mounted on a sliding mechanism on the other. The slide scans across a receiving shuttle dropping one row of pins at a time until a total scan of the slide includes a complete pin matrix. The completed pin matrix is then dropped from the slide into the carrier.
Problems with existing feeders include frequent bending of pins and jamming of pins in delivery tubes. Music wire is typically run down into the jammed tube in an attempt to clear the jam. In some cases the mechanism has to be disassembled and cleared. There is risk that use of music wire will cause damage to the tube and tube assembly.
With small pins, static cling can be generated from the friction between the pins and tubes as the pins typically travel about 2.5 feet down the tubes to the shuttle, resulting in jamming.
The row by row scan drop method relies on the pin dropping completely into the receiving hole of the shuttle before the slide reaches the far side of the hole. Pins are sheared off or bent if the pin does not drop completely into the hole, and the mechanism must be cleared or disassembled before continued operation. A proclivity to jam necessitates frequent operator intervention, continual operator vigilance and component waste.
An additional problem is presented by a new high density product, which features interstitial patterns. The proximity of the pins to each other, the number of pins and their interstitial arrangement make previous methods of pin feeding obsolete. Tubes cannot be positioned close enough to each other in order to accomplish interstitial pinning in a high density matrix grid.